Plurihormonal (TSH-GH-prolactin Secreting) PIT-1-Positive pituitary Macroadenoma/Pituitary Neuroendocrine Tumor (PitNET) Associated with Graves’ Disease: A Case Report

Background: Differential diagnosis of primary and secondary hyperthyroidism can be challenging. Moreover, although extremely rare, the two conditions can coexist. Case Presentation: A 58-year-old woman presented with symptoms of thyrotoxicosis, gradual changes in face shape, headache and progressive enlargement of hands and feet in the last year. When she was 46 years old, she was diagnosed with Graves’ disease, and treated with 4-year methimazole therapy. Since 2016, a progressive increase of free-T4 and free-T3 with normal-TSH and positive TrAb was noticed. Results: At biochemical examination, fT3 was 5.3pg/ml (n. v. 2.5 - 3.9 pg/ml), fT4 was 20.6 pg/ml (n.v 6-12 pg/ml), IGF1 was 698 ng/ml (57 – 240 ng/ml*), GH (basally and after OGTT), and prolactin were significantly increased; while TSH was 1.8 (n.v. 0.35-4.0 mcUI/ml). A pituitary MRI demonstrated a large sellar tumor with suprasellar extension. The patient underwent endoscopic transsphenoidal surgery. Histological examination revealed a plurihormonal (GH-PRLTSH- secreting) PIT-1-positive pituitary adenoma/pituitary neuroendocrine tumor (PitNET). At 3- month follow-up, the pituitary function was normal, and no residual tumor was detected at the MRI. Conclusion: We report a rare case of Graves’ disease coexisting with a plurihormonal PIT-1-positive pituitary adenoma/PitNET.